Alkaline Bacillus amylase

ABSTRACT

This invention relates to an amylase derived from  Bacillus horikoshii . The amylase has a preference for soluble substrates, shows substantial exo-amylase activity and has a pH optimum of about 9.8.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 11/721,353 filed Jun. 11, 2007, now U.S. Pat. No. 7,659,101, whichis a 35 U.S.C. 371 national application of PCT/DK2005/000794 filed onDec. 15, 2005, which claims priority or the benefit under 35 U.S.C. 119of Danish application no. PA 2004 01936 filed on Dec. 15, 2004 and U.S.provisional application No. 60/636,212 filed on Dec. 15, 2004, thecontents of which are fully incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to amylases having a pH optimum around9.8.

BACKGROUND OF THE INVENTION

For a number of years alpha-amylase enzymes have been used for a varietyof different purposes, the most important of which are starchliquefaction, textile desizing, starch modification in the paper andpulp industry, and for brewing and baking.

Examples of commercial alpha-amylase products are Termamyl®, BAN® andFungamyl®, all available from Novozymes NS, Denmark. These and similarproducts from other commercial sources have an acidic to a neutral pHoptimum, typically in the range of from pH 5 to pH 7.5, and they do notdisplay optimal activity in detergent solutions at alkaline pH.

WO 95/26397 discloses an alpha-amylase from a Bacillus strain, which hasoptimum activity at pH 8. WO 96/23873 describes variants of Bacillusamylases with improved performance under washing conditions.

U.S. Pat. No. 5,147,796 describes an alkaline pullulanase havingalpha-amylase activity. FIG. 2 b of the document shows optimum amylaseactivity at pH 8-8.5.

M. Takagi et al., J. Ferment. Bioeng, vol 81, No. 6, 557-559 (1996)describe an alkaliphilic alpha-amylase-pullulanase from Bacillus sp. Theenzyme has optimum amylase activity at pH 9, but the activity dropsrapidly at higher pH, and the activity at pH 10 is lower than at pH 7.

WO 01/14532 and WO 99/50399 disclose alpha-amylases from Bacillusstrains, which have optimum activity at pH 9.5.

The amylase of the present invention has a highly alkaline profile withan optimum activity at pH 9.8

SUMMARY OF THE INVENTION

The invention provides an alpha-amylase having one or more of thefollowing characteristics:

-   -   a) An amino acid sequence which has at least 60% identity with        amino acids 1 to 1105 of Seq Id No: 2.    -   b) An amino acid sequence comprising Seq Id No: 2.    -   c) An amino acid sequence that is identical to Seq Id No: 2.    -   d) An amino acid sequence comprised by Seq Id No: 2

In a further aspect the invention relates to an alpha-amylase having oneor more characteristics selected from the group consisting of:

-   -   a) a theoretical pI of about 4.4; or    -   b) a pH-optimum of about 9.8; or    -   c) a temperature optimum of about 50° C. at pH 9; or    -   d) at least 40% residual activity after 30 minutes at 50° C. and        pH 10; or    -   e) exhibits substantial exo-amylase activity    -   f) obtainable from Bacillus horikoshii.

In a further aspect the invention relates to an alpha-amylase encoded bya polynucleotide which hybridizes under medium stringency conditions,more preferably high stringency conditions, with the nucleic acidsequence of Seq Id No:1 or its complementary strand.

In a still further aspect the invention relates to a DNA sequenceencoding the alpha-amylase of the invention. I a particular embodimentsaid DNA sequence comprises or is comprised by Seq. ID No.: 1.

Further aspects of the invention provide a recombinant expression vectorcomprising the DNA sequence, and a cell transformed with the DNAsequence or the recombinant expression vector.

The invention also provides a method for producing the alpha-amylase andfor the use of said alpha-amylase for production ofmalto-oligosaccharides with a DP of less than 10, and as a detergentenzyme.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a pH activity profile of the alpha-amylase of theinvention.

FIG. 2 shows a temperature activity profile of the alpha-amylase of theinvention.

FIG. 3 shows the stability of the alpha-amylase of the invention afterincubation at various temperatures.

FIG. 4 shows the stability of the alpha-amylase of the invention afterincubation at various pH.

FIG. 5 shows the wash performance of the alpha-amylase in a commercialdetergent.

FIG. 6 shows the wash performance of the alpha-amylase at pH 9 inCarbonate buffer.

DETAILED DESCRIPTION OF THE INVENTION

Sequence Listing and Deposited Microorganisms

The present application contains information in the form of a sequencelisting, which is appended to the application and also submitted on adata carrier accompanying this application. In addition, the presentapplication refers to deposited microorganisms. The contents of the datacarrier and the deposited microorganisms are fully incorporated hereinby reference.

The alpha-amylase of the invention may be derived from Bacillus sp.strain NCIB 12512. This strain was deposited on 29 Jul. 1987 under theterms of the Budapest Treaty on the International Recognition of theDeposit of Microorganisms for the Purposes of Patent Procedure at theNational Collections of Industrial and Marine Bacteria Limited (NCIMB),23 St. Machar Drive, Aberdeen AB2 1RY, Scotland, United Kingdom.

The deposit was made by Novo Nordisk NS and was later assigned toNovozymes NS.

Production of Alpha-Amylase

The alpha-amylase of the invention can be produced by cultivating asuitable amylase-producing strain of Bacillus or the transformed hostcell of the invention in a suitable nutrient medium, and recovering thealpha-amylase from the culture medium.

The medium used to cultivate the cells may be any conventional mediumsuitable for growing the host cell in question and obtaining expressionof the alpha-amylase of the invention. Suitable media are available fromcommercial suppliers or may be prepared according to published recipes(e.g. as described in catalogues of the American Type CultureCollection).

The alpha-amylase secreted from the host cells may conveniently berecovered from the culture medium by well-known procedures, includingseparating the cells from the medium by centrifugation or filtration,and precipitating proteinaceous components of the medium by means of asalt such as ammonium sulphate, followed by the use of chromatographicprocedures such as ion exchange chromatography, affinity chromatography,or the like.

Properties of Alpha-Amylase

A preferred alpha-amylase is derived from Bacillus horikoshii. It can beproduced as described in the examples. The full length amino acidsequence of the amylase and the DNA encoding it are shown in Seq. ID No.2 and Seq. ID No. 1 respectively.

In the present context, “derived from” is intended not only to indicatean alpha-amylase produced or producible by a strain of the organism inquestion, but also an alpha-amylase encoded by a DNA sequence isolatedfrom such strain and produced in a host organism transformed with saidDNA sequence. Finally, the term is intended to indicate analpha-amylase, which is encoded by a DNA sequence of synthetic and/orcDNA origin and which has the identifying characteristics of thealpha-amylase in question.

The following characteristics were found for the amylase of theinvention (purified alpha-amylase):

-   A molecular weight of approximately 130 kDa as determined by    SDS-PAGE using a Novex, 4-20% gradient gel. The theoretical MW of    the polypeptide chain is 123 kDa, using the pc program GPMAW    (Lighthouse data).-   A theoretical pI of 4.4 was determined by the pc program Vector NTI    8, 1994-2002 Infomax, Inc.-   A pH-activity curve is shown in FIG. 1, taking the activity at pH    9.8 as 100%. It was determined using the reducing sugar assay    (PAHBAH) using 50 mM Britten-Robinson buffer adjusted to various    pH-values. FIG. 1 shows that the optimum activity is about pH 9.8.-   A temperature-activity curve was measured using the PAHBAH assay at    various temperatures with 50 mM Britten-Robinson buffer adjusted to    pH 9.0. The results are shown in FIG. 2. It is seen from FIG. 2 that    the amylase of the invention has optimum activity at about 50° C.-   Temperature stability of the amylase was measured at pH 10. A    stability profile of the amylase of the invention (FIG. 3) shows    superior stability of the amylase of the invention compared to a    commercial amylase.-   pH stability of the amylase was measured at 37° C. A stability    profile of the amylase of the invention (FIG. 4) shows superior    stability of the amylase of the invention compared to a commercial    amylase.    Sequence Homology and Alignment

For purposes of the present invention, alignments of sequences andcalculation of homology and identity scores may be done using a fullSmith-Waterman alignment, useful for both protein and DNA alignments.The default scoring matrices BLOSUM50 and the identity matrix are usedfor protein and DNA alignments respectively. The penalty for the firstresidue in a gap is −12 for proteins and −16 for DNA, while the penaltyfor additional residues in a gap is −2 for proteins and −4 for DNA.Alignment may be made with the FASTA package version v20u6 (W. R.Pearson and D. J. Lipman (1988), “Improved Tools for Biological SequenceAnalysis”, PNAS 85:2444-2448, and W. R. Pearson (1990) “Rapid andSensitive Sequence Comparison with FASTP and FASTA”, Methods inEnzymology, 183:63-98).

Multiple alignments of protein sequences may be made using “ClustalW”(Thompson, J. D., Higgins, D. G. and Gibson, T. J. (1994) CLUSTAL W:improving the sensitivity of progressive multiple sequence alignmentthrough sequence weighting, positions-specific gap penalties and weightmatrix choice. Nucleic Acids Research, 22:4673-4680). Multiplealignments of DNA sequences may be done using the protein alignment as atemplate, replacing the amino acids with the corresponding codon fromthe DNA sequence.

The amino acid sequence of the present invention exhibits a degree ofidentity preferably of at least 60%, or at least 65%, or at least 70%,or at least 75%, preferably at least 80%, or at least 85%, morepreferably at least 90%, especially at least 95%, even more especiallyat least 96%, or at least 97%, or at least 98%, or at least 99% with theamino acid sequence shown in positions 1-1105 of SEQ ID NO: 2.

The DNA construct of the present invention comprises a DNA sequenceexhibiting a degree of identity preferably of at least 60%, preferablyat least 70%, more preferably at least 80%, especially at least 90% orat least 95%, even more especially at least 97% or at least 99% with thenucleic acid sequence shown in positions 109-3423 of SEQ ID NO: 1.

Hybridization

Suitable experimental conditions for determining hybridization between anucleotide probe and a homologous DNA or RNA sequence involvespresoaking of the filter containing the DNA fragments or RNA tohybridize in 5×SSC (sodium chloride/sodium citrate, Sambrook, et al.,1989) for 10 min, and prehybridization of the filter in a solution of5×SSC, 5× Denhardt's solution (Sambrook, et al., 1989), 0.5% SDS and 100μg/ml of denatured sonicated salmon sperm DNA (Sambrook, et al., 1989),followed by hybridization in the same solution containing arandom-primed (Feinberg, A. P. and Vogelstein, B. (1983) Anal. Biochem.132:6-13), 32P-dCTP-labeled (specific activity>1×109 cpm/μg) probe for12 hours at ca. 45° C. The filter is then washed twice for 30 minutes in2×SSC, 0.5% SDS at least 55° C. (low stringency), preferably at least60° C. (medium stringency), more preferably at least 65° C. (medium/highstringency), more preferably at least 70° C. (high stringency), evenmore preferably at least 75° C. (very high stringency).

Molecules which hybridize to the oligonucleotide probe under theseconditions are detected by exposure to x-ray film.

Recombinant Expression Vector

The present invention also relates to recombinant expression vectorscomprising a polynucleotide of the present invention, a promoter, andtranscriptional and translational stop signals. The various nucleicacids and control sequences described above may be joined together toproduce a recombinant expression vector which may include one or moreconvenient restriction sites to allow for insertion or substitution ofthe nucleotide sequence encoding the polypeptide at such sites.Alternatively, a nucleotide sequence of the present invention may beexpressed by inserting the nucleotide sequence or a nucleic acidconstruct comprising the sequence into an appropriate vector forexpression. In creating the expression vector, the coding sequence islocated in the vector so that the coding sequence is operably linkedwith the appropriate control sequences for expression.

The recombinant expression vector may be any vector (e.g., a plasmid orvirus) which can be conveniently subjected to recombinant DNA proceduresand can bring about expression of the nucleotide sequence. The choice ofthe vector will typically depend on the compatibility of the vector withthe host cell into which the vector is to be introduced. The vectors maybe linear or closed circular plasmids.

The vector may be an autonomously replicating vector, i.e., a vectorwhich exists as an extrachromosomal entity, the replication of which isindependent of chromosomal replication, e.g., a plasmid, anextrachromosomal element, a minichromosome, or an artificial chromosome.The vector may contain any means for assuring self-replication.Alternatively, the vector may be one which, when introduced into thehost cell, is integrated into the genome and replicated together withthe chromosome(s) into which it has been integrated. Furthermore, asingle vector or plasmid or two or more vectors or plasmids whichtogether contain the total DNA to be introduced into the genome of thehost cell, or a transposon may be used.

The vectors of the present invention preferably contain one or moreselectable markers which permit easy selection of transformed cells. Aselectable marker is a gene the product of which provides for biocide orviral resistance, resistance to heavy metals, prototrophy to auxotrophs,and the like.

Examples of bacterial selectable markers are the dal genes from Bacillussubtilis or Bacillus licheniformis, or markers which confer antibioticresistance such as ampicillin, kanamycin, chloramphenicol, ortetracycline resistance.

The vectors of the present invention preferably contain an element(s)that permits integration of the vector into the host cell's genome orautonomous replication of the vector in the cell independent of thegenome.

For integration into the host cell genome, the vector may rely on thepolynucleotide's sequence encoding the polypeptide or any other elementof the vector for integration into the genome by homologous ornonhomologous recombination. Alternatively, the vector may containadditional nucleotide sequences for directing integration by homologousrecombination into the genome of the host cell at a precise location(s)in the chromosome(s). To increase the likelihood of integration at aprecise location, the integrational elements should preferably contain asufficient number of nucleic acids, such as 100 to 10,000 base pairs,preferably 400 to 10,000 base pairs, and most preferably 800 to 10,000base pairs, which have a high degree of identity with the correspondingtarget sequence to enhance the probability of homologous recombination.The integrational elements may be any sequence that is homologous withthe target sequence in the genome of the host cell. Furthermore, theintegrational elements may be non-encoding or encoding nucleotidesequences. On the other hand, the vector may be integrated into thegenome of the host cell by non-homologous recombination.

For autonomous replication, the vector may further comprise an origin ofreplication enabling the vector to replicate autonomously in the hostcell in question. The origin of replication may be any plasmidreplicator mediating autonomous replication which functions in a cell.The term “origin of replication” or “plasmid replicator” is definedherein as a nucleotide sequence that enables a plasmid or vector toreplicate in vivo.

Examples of bacterial origins of replication are the origins ofreplication of plasmids pBR322, pUC19, pACYC177, and pACYC184 permittingreplication in E. coli, and pUB110, pE194, pTA1060, and pAMR1 permittingreplication in Bacillus.

More than one copy of a polynucleotide of the present invention may beinserted into the host cell to increase production of the gene product.An increase in the copy number of the polynucleotide can be obtained byintegrating at least one additional copy of the sequence into the hostcell genome or by including an amplifiable selectable marker gene withthe polynucleotide where cells containing amplified copies of theselectable marker gene, and thereby additional copies of thepolynucleotide, can be selected for by cultivating the cells in thepresence of the appropriate selectable agent.

The procedures used to ligate the elements described above to constructthe recombinant expression vectors of the present invention are wellknown to one skilled in the art (see, e.g., Sambrook et al.: MolecularCloning: A Laboratory Manunal, Second Edition (1989) Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y.).

Host Cells

The cell of the invention, either comprising a DNA construct or anexpression vector of the invention as defined above, is advantageouslyused as a host cell in the recombinant production of the alpha-amylaseof the invention. The cell may be transformed with the DNA construct ofthe invention encoding the amylase, conveniently by integrating the DNAconstruct (in one or more copies) in the host chromosome. Thisintegration is generally considered to be an advantage as the DNAsequence is more likely to be stably maintained in the cell. Integrationof the DNA constructs into the host chromosome may be performedaccording to conventional methods, e.g. by homologous or heterologousrecombination. Alternatively, the cell may be transformed with anexpression vector as described above in connection with the differenttypes of host cells.

The cell of the invention may be a cell of a higher organism such as amammal or an insect, but is preferably a microbial cell, e.g., abacterial or a fungal (including yeast) cell. Examples of bacterial hostcells which, on cultivation, are capable of producing the enzyme of theinvention are gram positive bacteria such as strains of Bacillus, suchas strains of B. subtilis, B. licheniformis, B. lentus, B. clausii, B.brevis, B. stearothermophilus, B. alkalophilus, B. amyloliquefaciens, B.coagulans, B. circulans, B. lautus, B. megaterium or B. thuringiensis,or strains of Streptomyces, such as S. lividans or S. murinus, or gramnegative bacteria such as Escherichia coli. The transformation of thebacteria may be effected by protoplast transformation, electroporation,conjugation, or by using competent cells in a manner known per se (cf.Sambrook et al., 1989: Molecular Cloning: A Laboratory Mannual, SecondEdition (1989) Cold Spring Harbor Laboratory Press, Cold Spring Harbor,N.Y.).

The yeast organism may favourably be selected from a species ofSaccharomyces or Schizosaccharomyces, e.g. Saccharomyces cerevisiae. Thefilamentous fungus may advantageously belong to a species ofAspergillus, e.g., Aspergillus oryzae or Aspergillus niger. Fungal cellsmay be transformed by a process involving protoplast formation andtransformation of the protoplasts followed by regeneration of the cellwall in a manner known per se. A suitable procedure for transformationof Aspergillus host cells is described in EP 238 023.

Industrial Applications—Please Provide Information About RelevantApplications

Owing to their activity at alkaline pH values, the alpha-amylases of theinvention are well suited for use in a variety of industrial processes,e.g. laundry and hard surface cleaning detergent compositions, theproduction of sweeteners and ethanol from starch. Thus, it may be usedin conventional starch-converting processes, such as liquefaction andsaccharification processes described in U.S. Pat. No. 3,912,590 and EPpatent publications Nos. 252,730 and 63,909.

Pulp and Paper Production

The alkaline alpha-amylase of the invention may also be used in theproduction of lignocellulosic materials, such as pulp, paper andcardboard, from starch reinforced waste paper and cardboard, especiallywhere repulping occurs at pH above 7 and where amylases can facilitatethe disintegration of the waste material through degradation of thereinforcing starch. The alpha-amylase of the invention is especiallyuseful in a process for producing a papermaking pulp from starch-coatedprinted-paper. The process may be performed as described in WO 95/14807,comprising the following steps:

-   a) disintegrating the paper to produce a pulp,-   b) treating with a starch-degrading enzyme before, during or after    step a), and-   c) separating ink particles from the pulp after steps a) and b).

The alpha-amylases of the invention may also be very useful in modifyingstarch where enzymatically modified starch is used in papermakingtogether with alkaline fillers such as calcium carbonate, kaolin andclays. With the alkaline alpha-amylases of the invention it becomespossible to modify the starch in the presence of the filler thusallowing for a simpler integrated process.

Desizing

The alpha-amylase of the invention may also be very useful in textiledesizing. In the textile processing industry, alpha-amylases aretraditionally used as auxiliaries in the desizing process to facilitatethe removal of starch-containing size, which has served as a protectivecoating on weft yarns during weaving. Complete removal of the sizecoating after weaving is important to ensure optimum results in thesubsequent processes, in which the fabric is scoured, bleached and dyed.Enzymatic starch break-down is preferred because it does not involve anyharmful effect on the fibre material. In order to reduce processing costand increase mill throughput, the desizing processing is sometimescombined with the scouring and bleaching steps. In such cases,non-enzymatic auxiliaries such as alkali or oxidation agents aretypically used to break down the starch, because traditionalalpha-amylases are not very compatible with high pH levels and bleachingagents. The non-enzymatic breakdown of the starch size does lead to somefibre damage because of the rather aggressive chemicals used.Accordingly, it would be desirable to use the alpha-amylases of theinvention as they have an improved performance in alkaline solutions.The alpha-amylases may be used alone or in combination with a cellulasewhen desizing cellulose-containing fabric or textile.

Beer Making

The alpha-amylases of the invention may also be very useful in abeer-making process; the alpha-amylases will typically be added duringthe mashing process.

Production of Malto-Oligosaccharides

The alpha-amylase of the invention exhibits substantialexo-alpha-amylase (see break down pattern of amylase and waxy cornstarch, Example 4). This allows for the use of the enzyme of the presentinvention for production of malto-oligosaccharides of a specific degreeof polymerization (DP), a process that otherwise is tedious andexpensive. Malto-oligosaccharides with a DP around 10 or less havepotential applications in e.g. the food industry. Thesemalto-oligosaccharides have a less sweet taste compared to sucrose's,and a partial replacement of sucrose with e.g. maltotetraose (DP=4)reduces the sweetness of the foods without affecting their inherenttaste and flavour. At the same time they have a high moisture retentionpower, and can thus serve to prevent retrogradation of starch ingredientand makes retain a suitable moisture in foods. A further aspect ofapplication of malto-oligosaccharides is that they show a less Maillardreaction, and thus less coloration. Malto-oligosaccharides show higherviscosity than that of sucrose, and are useful in improving the textureof foods. A further aspect of the application of malto-oligosaccharidesis that they may be used to control the freezing points of frozen foods,as they depresses the freezing point of water more moderately thansucrose or high-fructose syrup.

Detergent Compositions

The alpha-amylase of the invention may be added to and thus become acomponent of a detergent composition.

The detergent composition of the invention may for example be formulatedas a hand or machine laundry detergent composition including a laundryadditive composition suitable for pre-treatment of stained fabrics and arinse added fabric softener composition, or be formulated as a detergentcomposition for use in general household hard surface cleaningoperations, or be formulated for hand or machine dishwashing operations.

In a specific aspect, the invention provides a detergent additivecomprising the enzyme of the invention. The detergent additive as wellas the detergent composition may comprise one or more other enzymes suchas a protease, a lipase, a cutinase, an amylase, a carbohydrase, acellulase, a pectinase, a mannanase, an arabinase, a galactanase, axylanase, an oxidase, e.g., a laccase, a pectate lyase, and/or aperoxidase.

In general the properties of the chosen enzyme(s) should be compatiblewith the selected detergent, (i.e., pH-optimum, compatibility with otherenzymatic and non-enzymatic ingredients, etc.), and the enzyme(s) shouldbe present in effective amounts.

The detergent enzyme(s) may be included in a detergent composition byadding separate additives containing one or more enzymes, or by adding acombined additive comprising all of these enzymes. A detergent additiveof the invention, i.e., a separate additive or a combined additive, canbe formulated, e.g., granulate, a liquid, a slurry, etc. Preferreddetergent additive formulations are granulates, in particularnon-dusting granulates, liquids, in particular stabilized liquids, orslurries.

Non-dusting granulates may be produced, e.g., as disclosed in U.S. Pat.Nos. 4,106,991 and 4,661,452 and may optionally be coated by methodsknown in the art. Examples of waxy coating materials are poly(ethyleneoxide) products (polyethyleneglycol, PEG) with mean molar weights of1000 to 20000; ethoxylated nonyl-phenols having from 16 to 50 ethyleneoxide units; ethoxylated fatty alcohols in which the alcohol containsfrom 12 to 20 carbon atoms and in which there are 15 to 80 ethyleneoxide units; fatty alcohols; fatty acids; and mono- and di- andtriglycerides of fatty acids. Examples of film-forming coating materialssuitable for application by fluid bed techniques are given in GB1483591. Liquid enzyme pre-parations may, for instance, be stabilized byadding a polyol such as propylene glycol, a sugar or sugar alcohol,lactic acid or boric acid according to established methods. Protectedenzymes may be prepared according to the method disclosed in EP 238,216.

The detergent composition of the invention may be in any convenientform, e.g., a bar, a tablet, a powder, a granule, a paste or a liquid. Aliquid detergent may be aqueous, typically containing up to 70% waterand 0-30% organic solvent, or non-aqueous.

The present invention is further described by the following examples,which should not be construed as limiting the scope of the invention.

Materials and Methods

50 mM Britton-Robinson Buffer

50 mM acetic acid, 50 mM phosphoric acid, 50 mM boric acid, pH adjustedto the value of interest with NaOH.

Detergent:

Commercial European color detergent; alpha-amylases present in thedetergent were inactivated by microwaves before adding the alpha-amylaseof the present invention.

EXAMPLES Example 1 Cloning and Expression of the Alpha-Amylase of theInvention

Bacterial Strains and Growth Conditions

TH1 is a Bacillus subtilis strain (amy-, spo-, apr-, npr-), that hasbeen modified by insertion of a construct, from the strain DN3 (Noone etal. 2000, J Bacteriol 182 (6) 1592-1599) by transformation and selectionfor erytromycin. The changed genotype is: ykdA::pDN3 (PykdA-lacZPspac-ykdA) Ermr. TH1 contains the following features: the full ykdApromoter is fused to the LacZ reporter gene. In addition the ykdA geneis placed under control of the IPTG-inducible Pspac promoter, so theykdA gene no longer has it's naturally regulation. The strain can beused as host for expression clones and libraries and transformantsexpressing and secreting protein can be selected on plates containingX-gal and IPTG. TH1 can be maintained and propagated in Luria-Bertani(LB) or supplemented with agar (1.5% wt/vol) as appropriate, addition of6 μg/ml erythromycin and grown at 37° C. with aeration.

DNA Manipulations

Bacillus subtilis transformations were performed as described previously(Anagnostopolous, C., and J. Spizizen. 1961. Requirements fortransformation in Bacillus subtilis. J. Bacteriol. 81:741-746). Allroutine molecular biological procedures were performed according to theprotocols described by Sambrook et al. (1989).

Modification of Vector

The shuttle vector for Bacillus and E. coli pDG268neo (Widner B; ThomasM; Sternberg D; Lammon D; Behr R; Sloma A (2000): Development ofmarker-free strains of Bacillus subtilis capable of secreting highlevels of industrial enzymes. Journal of Industrial Microbiology andBiotechnology, Vol. 25 (4) pp. 204-212) was modified to allow forcloning of partial digested Sau3A or Tsp509I genomic DNA. The vector wasmodified by inserting a BamHI and EcoRI site between the Sac1 and Not1sites (fragment between was deleted and a linker was inserted). In thisway genomic fragments can be cloned and genes contained in thesefragments can be transcribed from either the strong promoter on thevector or by their own promoter.

Construction of a Library in E. coli

Chromosomal DNA from Bacillus horikoshii was isolated by QIAmp TissueKit (Qiagen, Hilden, Germany). The genomic DNA was partial digested bySau3A by standard methods. DNA fragments from 3-5 kb were gel purifiedand ligated into BamHI digested and dephosphorylated vector (themodified pDG268neo (=pDG268BE)). 1 micro L of the ligation wastransformed by electroporation into competent E. coli cells (ElectromaxDH10B Cells, Invitrogen) according to standard protocols. Thetransformed cells were plated on plates containing solid LB mediacontaining ampicillin as selection marker. The plates were incubated for16 h at 37 C. 20.000 transformants obtained this way were pooled andplasmid DNA was prepared from the pooled cells by using a midiprepQiagene kit (Qiagene). This plasmid pool represents the library.

Transformation of Library into Bacillus subtilis TH1

The obtained plasmid pool DNA was used to transform Bacillus TH1competent cells. Bacillus transformations were plated on Petri disheswith LB-media supplemented with agar (1.5% wt/vol) and X-Gal(5-bromo-4-chloro-3-indolyl-b-D-galactopyranoside) was added to themedia at a concentration of 64 micro g/mL, and IPTG(isopropyl-b-D-thiogalactopyranoside) was added to a final concentrationof 0.8 mM. Antibiotics were added at the following concentrations:chloramphenicol, 6 μg/ml; and erythromycin, 3 μg/ml. Transformants wereincubated at 37° C. overnight.

Selection and Analysis of Transformants Secreting Recombinant Protein

Blue colonies that occurred after 16 h of incubation or in the following24 h were selected and restreaked on new plates to obtain pure singleblue colonies. For expression studies transformants were grown in liquidPS-1 or TY media at 30° C. and at 250 rpm. Cells were spun down and thesupernatant analyzed for secreted recombinant protein onSDS-polyacrylamide gels.

Results

A genomic library of Bacillus horikoshii was made in the vectorpDGneo268BE. A plasmid pool was made from the E. coli library. Theplasmid pool DNA was transformed into Bacillus strain TH1 (TH1 allowsfor blue/white selection of secreting recombinant clones).16-20000Bacillus transformants were obtained on agar plates containing X-gal andIPTG, which allows for blue/white selection of secreting Bacillustransformants. Nineteen intense blue colonies appeared among the16-20.000 colonies. These blue colonies were fermented in liquid mediaand the supernatants analyzed on SDS-gels. 5 of the 19 blue coloniesgave an intense protein band on a SDS gel. A recombinant protein band ofaround 120 kD from one of the clones was purified and characterized byN-terminal amino acid sequencing. The DNA insert in the correspondingclone was sequenced to identify the gene giving rise to the recombinantprotein band. The resulting gene sequence is the sequence of the alphaamylase of the invention listed as the Seq. ID No.:1 and the encodedprotein is listed as the Seq. ID No: 2.

Example 2 Purification Method for the Alpha-Amylase of the Invention

The culture supernatant was centrifuged and cell debris was discarded.

Fermentation supernatant was then sterile filtered using Seitz-EKSfilter with pore size 0.22 microns which was purchased from Pall SeitzSchenk Filter system GmbH, Bettringer Strasse 42 D-73550 Germany.Filtration was carried out using pressure filter.

The sterile filtered supernatant was then adjusted to 1 M ammoniumsulphate by adding solid ammonium sulphate.

Hydrophobic chromatography on Matrix Phenyl Toyopearl 650M Toshohaas waspurchased from Bie and Berntsen Roedovre, Denmark.

Fifty milliliter column was packed with the matrix and equilibrated with1M ammonium sulphate adjusted to pH 8. Sterile filtered fermentationsupernatant was then applied on the column and washed with the 1 Molarammonium sulphate solution till all unbound material was washed out.

Bound Proteins were then eluted by lowering the salt concentration using50 mM Borate pH 8 solution without any salt. Fractions 10 ml each werecollected and analyzed by SDS-PAGE.

Fractions containing protein with 120 kDa molecular weight were thenpooled and dialyzed against Buffer containing 50 mM Borate, 5 mMDimethyl glutaric acid pH 6.

Anion exchange chromatography on Fast flow Q sepharose matrix waspurchased form Amersham Pharmacia and 50 ml column was packed. Thecolumn was then equilibrated with the buffer containing 50 mM Boarte, 5mM Dimetrhyl glutaric acid pH6. The dialyzed pool containing the 120 kDaprotein was then applied on the column and washed with the buffer tillall unbound material was washed out. The bound protein was then elutedwith linear salt gradient using Buffer B pH6 which contained 50 mMBorate, 5 mM Dimethyl glutaric acid and 1 M salt.

Fractions were then analyzed by SDS-PAGE and pooled on the basis ofMolecular weight which contained the desired protein.

Example 3 Characterization of the Alpha-Amylase of the Present Invention

Reducing Sugar Assay (PAHBAH)

The enzyme reaction was initiated by adding 50 μl enzyme sample to 100micro L 0.15% amylose (Merck, 4561), 50 mM Britton-Robinson buffer (50mM acetic acid, 50 mM phosphoric acid, 50 mM boric acid, pH adjusted tothe value of interest with NaOH), 0.01% Triton-X-100 in PCR tubes. Thissolution was incubated for 15 min at different temp. in a PeltierThermal Cycler (PCT-200, MJ research) and stopped with 75 micro L 1.5%(w/v) p-hydroxybenzoic acid hydrazide (Sigma, H-9882), 5% (w/v)K-Na-tartrate (Merck, 1.08087), 2% (w/v) NaOH and incubated at 95° C.for 10 min. The temperature was lowered to 20° C. and 150 micro L wastransferred to a 96 well micro titter plate. The absorbance was thenmeasured at 410 nm with a microplate reader (Spectra Max 190, MolecularDevices).

pH Profile

The pH profile was measured at 37° C., at pH 2, 3, 4, 5, 6, 7, 8, 9, 10,11 and 12 using the Reducing sugar assay described above.

The pH profile is shown in FIG. 1, and it is seen that the alpha-amylaseof the invention has an optimum activity at about 9.8.

Temperature Profile

The temperature profile was measured at pH 9 at 20° C., 30° C., 40° C.,50° C., 60° C., 70° C., 80° C., 90° C. using the Reducing sugar assaydescribed above.

The temperature profile is shown in FIG. 2, and it is seen that thealpha-amylase of the invention has an optimum activity at about 50° C.

Temperature Stability

150 micro L enzyme sample (diluted with 50 mM Britton-Robinson buffer:50 mM acetic acid, 50 mM phosphoric acid, 50 mM boric acid, pH adjustedto 10 with NaOH, with 1 mM EDTA or 1 mM CaCl₂) in an Eppendorf tube wasincubated for 30 min a in Eppendorf Thermomixer at differenttemperatures and 300 rpm shaking. The incubation was stopped bytransferring the eppendorf tupe to an ice bath and adding 75 micro Lsolution to 75 micro L 0.5 M HEPES pH 7.20 micro L of the above stoppedsolution was transferred into a microtiter plate and 200 micro L 3.7 mM4,6-ethylidene-G₇PNP, 3.3 kU/L alpha-glucosidase, 52.2 mM HEPES, 73 mMNaCl, 10.5 mM MgCl2, 0.06 mM CaCl₂, pH 7 (AMYL kit, Roche DiagnosticsGmbH). The absorbance at 405 nm was measured with 11 seconds intervalswith a microplate reader (Spectra Max 190, Molecular Devices) and theactivity was determined from the slope generated after 5 minutesmeasurement.

The temperature stability is depicted in FIG. 3, where the stability ofthe amylase of the present invention is compared with the stability ofthe commercially available amylase BAN®, available from Novozymes NS.FIG. 3 shows a superior stability of the amylase of the presentinvention as compared to the commercially available amylase.

pH Stability

150 micro L enzyme sample (diluted with 50 mM Britton-Robinson buffer(50 mM acetic acid, 50 mM phosphoric acid, 50 mM boric acid, pH adjustedto the value of interest with NaOH, with and without 1 mM CaCl₂)) in anEppendorf tube was incubated for 30 minutes in a Eppendorf Thermomixerat 37° C. and 300 rpm shaking. The incubation was stopped bytransferring 75 micro L solution to 75 micro L 0.5 M HEPES pH 7. 20micro L of the above stopped solution was transferred into a microtiterplate and 200 μl 3.7 mM 4,6-ethylidene-G₇PNP, 3.3 kU/Lalpha-glucosidase, 52.2 mM HEPES, 73 mM NaCl, 10.5 mM MgCl2, 0.06 mMCaCl₂, pH 7(AMYL kit, Roche Diagnostics GmbH). The absorbance at 405 nmwas measured with 11 seconds intervals with a micro plate reader(Spectra Max 190, Molecular Devices) and the activity was determinedfrom the slope generated after 5 minutes measurement.

The pH stability is depicted in FIG. 4, where the stability of theamylase of the present invention is compared with the stability of thecommercially available amylase BAN®, available from Novozymes NS. FIG. 4shows a superior stability of the amylase of the present invention ascompared to the commercially available amylase.

pI Determination

The pI of the polypeptide chain is determined theoretically by the pcprogram Vector NTI 8, 1994-2002 Infomax, Inc. pI was determined to 4.4.

Example 4 Amylose/Starch Degradation Pattern

20 micro L sample were added to 1 mL 1% amylose (Merck, 4561) or 1% waxycorn starch (Cerestar), 10 mM sodium borate buffer, 0.1 mM CaCl₂, pH 9and incubated for various times at 37° C. The reaction was stopped byadding 20 micro L 1 M HCl and incubated at 95° C. for 10 minutes. Thesamples were filtered through a 0.22 micro meter filter and thecarbohydrate composition was determined by IMPC HPLC.

The data below is expressed in % area in a top in the HPLC chromatogram,compared to total area of all oligosaccharides in the 1035 minuteschromatogram.

TABLE 1 Degradation pattern of 1% amylose. 1% amylose degradationpattern 0 min 17 min 45 min 120 min 1035 min % % % % % DP6 <1 3 5 8 <1DP5 <1 0 1 1 <1 DP4 <1 2 6 15 48 DP3 <1 <1 <1 1 5 DP2 <1 1 2 6 26 DP1 <11 1 3 17

TABLE 2 Degradation pattern of 1% waxy corn starch. 1% waxy corn starch0 min 17 min 45 min 120 min 1035 min % % % % % DP6 <1 8 11 8 2 DP5 <1 <11 2 1 DP4 <1 3 7 18 30 DP3 <1 <1 <1 <1 5 DP2 <1 1 3 8 19 DP1 <1 1 1 4 14

During amylose/amylopectin degradation no DP products larger than DP6 isseen. Initially the domination degradation product is DP6 and afterprolonged incubation, this DP6 is hydrolyzed to DP4 and DP2. Thus, thisamylase exhibits substantially exo alpha amylase activity.

Example 5 Wash Performance of the Amylase of the Invention

Wash in Detergent Solution.

Washing performance is evaluated by washing starch-soiled CS-28 swatches(obtainable from CFT, Centre for Test Material, Netherlands) in a beakerunder constant shaking.

4 g/L of a commercially available detergent (Mega Perls Color fromHenkel GmbH) is added to water. Water hardness is adjusted to 15° dH byaddition of Ca:Mg in the ratio 4:1 prior to the addition of thedetergent. pH is not adjusted upon addition of detergent.

The soiled swatches are washed for 20 minutes at 40° C. Upon drying thereflectance is measured.

As can be seen from FIG. 5 the alpha-amylase of the invention clearly isable to remove starch from the soiled swatches.

Wash in Buffer Solution.

Washing performance is evaluated by washing starch-soiled CS-28 swatches(obtainable from CFT, Centre for Test Material, Netherlands) in a beakerunder constant shaking.

5 mM Carbonate buffer is used to adjust pH to 9.

The soiled swatches are washed for 20 minutes at 40° C. Upon drying thereflectance is measured.

As can be seen from FIG. 6 the alpha-amylase of the invention clearly isable to remove starch from the soiled swatches.

1. An isolated alpha-amylase comprising an amino acid sequence which hasat least 90% identity with amino acids 1 to 1105 of SEQ ID NO:
 2. 2. Thealpha-amylase of claim 1 having one or more characteristics selectedfrom the group consisting of: a) a theoretical pl of about 4.4; b) apH-optimum of about 9.8; c) a temperature optimum of about 50° C. at pH9; d) at least 40% residual activity after 30 minutes at 50° C. and pH10; or e) obtained from Bacillus horikoshii.
 3. An isolatedalpha-amylase encoded by a nucleic acid sequence which hybridizes underhigh stringency conditions with the complement of the nucleic acidsequence of SEQ ID NO; 1, wherein the high stringency conditions aredefined as prehybridization and hybridization in 5×SSC, 5× Denhardt'ssolution, 0.5% SDS and 100 pg/ml of denatured sonicated salmon sperm DNAat 45° C., followed by washing two times for 30 minutes using 2×SSC,0.2% SDS at 65° C.
 4. An isolated DNA sequence encoding thealpha-amylase of claim
 1. 5. A recombinant expression vector comprisingthe DNA sequence according to claim
 4. 6. A detergent compositioncomprising the alpha-amylase of claim
 1. 7. A cell transformed with aDNA sequence in accordance with claim
 4. 8. A cell transformed with arecombinant expression vector of claim
 5. 9. A cell in accordance withclaim 7, wherein the cell is a bacterial, fungal or yeast cell.
 10. Amethod of producing an alpha-amylase comprising: cultivating a celltransformed with a DNA sequence encoding an alpha-amylase comprising anamino acid sequence which has at least 90% identity with amino acids 1to 1105 of SEQ ID NO: 2 under conditions permitting the production ofthe alpha-amylase.
 11. The method of claim 10 further comprisingrecovering the alpha-amylase of the culture.
 12. The method inaccordance with claim 10, wherein said transformed cell selected fromthe group consisting of bacteria and fungi, and recovering thealpha-amylase from the culture medium.
 13. The method in accordance toclaim 12, wherein the transformed cell is yeast.